Field of the Invention
The present invention relates to a method and a system for protecting a transformer from catching fire. More particularly, the present invention relates to the method and system for detecting and preventing the fire generated in the transformers due to internal faults.
Description of the Related Art
Generally high voltage industrial transformers are manufactured of steel core and windings of a conducting material. The conducting material is covered with insulating materials such as paper. The transformers may also include other kind of insulating materials such as oil, generally enclosed in a metallic transformer tank. The oil is also used for the cooling of the transformers. The oil and other conducting materials used for the insulation are combustible.
In various applications, the transformers are used heavily for a longer time period and in extreme conditions such as at higher outside temperature, etc. Thus, the occurrence of some kind of fault or deterioration is quite common in transformers. These faults can be caused by voltage overloads, voltage surges, progressive deterioration of the insulation, insufficient oil levels, use of faulty dielectric materials, due to loose connections in joints of transformers, the appearance of moisture or the failure of an insulating component, and so forth. In the event of deterioration, there is a possibility of short circuit with other phases, or short circuit with respect to earth or within the winding. The short circuit causes abnormal currents to flow through the transformer windings. These kinds of failures can cause insulation failure and hence an electrical arc will get generated, which generates heat and a pressure wave inside the transformer which can cause the transformer tank to explode. Since the transformers are expensive equipment, a close and careful attention must be paid to prevent the explosion and fire.
Various methods have been used in the art to protect the transformer from catching fire. Various kinds of safety valves have been installed, which open up automatically in case of an emergency. However, these valves are not a fool-proof method for the protection of the transformers.
U.S. Pat. No. 5,946,171 discloses a method and device for prevention against explosion and fire of electrical transformers. The pressure generation inside the transformer tank is sensed. If the sensed value moves out a predefined threshold, the oil from the tank is drained and an inert gas is injected in the transformer tank to prevent fire. This method makes it possible to prevent the enclosure of the transformer from exploding up to some extent. However, the said method does not provide an indication in advance to take corrective measures. Also, by the time the corrective action takes place, a significant amount of electrical insulation breaks down.
European patent 2,232,510 provides another method for preventing, protecting an OLTC from fire and/or a transformer from explosion. In this patent, the fault is detected by sensing the incoming and outgoing currents of the transformer, along with it by sensing pressure rise through oil surge relay. As soon as the fault is detected, the transformer drains some quantity of oil and injects an inert gas to prevent fire. This method is helpful in preventing explosions in the transformer. However, the time taken for sensing the fire, i.e., the delay time is more. By the time the fire is detected, a lot of internal damage has already been occurred. There is need for providing a method which senses the fire accurately and as quickly as possible thereby reducing the delay time.
In addition to that, in both the methods, when the oil is drained from the transformer tank, it is drained to the external environment, which is hazardous. Thus a method is needed where the exposure of oil to the external environment and wastage of oil can be avoided.
While various other techniques have been used in the past for the prevention of fire in the transformer, there is still room for the development to provide even earlier detection of fire. Thus a need persists for the further contributions in this field of the technology.